The formula that you have written is the formula for acceleration.
A = Acceleration
FV = Final velocity
IV = Initial velocity
T = Time it took to change velocities
For example: Suppose that you are driving a car at 5 m/s. You then speed up to 35 m/s, and it took you 3 seconds to do that velocity change.
Put your known values into the equation.
A = (35 m/s - 5 m/s)/3 sec
A = (30 m/s)/3 seconds
A = 10 m/s/s
The unit is m/s/s, because the vehicle accelerated by 10 m/s each second. Sometimes using miles per hour helps students understand the unit better. I'll use the same numbers, but this time change the velocity unit.
A = (35 mi/hr - 5 mi/hr)/3 sec
A = (30 mi/hr)/3 seconds
A = 10 mi/hr/s
That means the car sped up by 10 miles per hour for each of the following 3 seconds.